1. Field of the Invention
The present invention relates to a thermosensitive biodegradable hydrogel, and more particularly, to a thermosensitive biodegradable hydrogel including methoxy polyethylene glycol-polycaprolactone (MPEG-PCL) to which a cell-adhesive peptide binds, and methoxy polyethylene glycol-polycaprolactone (MPEG-PCL).
2. Discussion of Related Art
As one new field that has emerged with the development of science, tissue engineering is a multidisciplinary science which involves an integrated application of fundamental concepts and scientific techniques from various fields of sciences such as life science, engineering, medical science, and the like, and an applied science which aims to understand the relationship between the structure and function of a biological tissue and also synthesize an artificial tissue which may be transplanted into the body in order to replace a damaged tissue or organ with a normal tissue or regenerate the damaged tissue or organ, thereby maintaining, improving or restoring the function of a human body.
Two representative tissue engineering techniques using hydrogel are summarized, as follows. One technique includes removing a desired tissue from a patient body, isolating cells from the removed tissue, proliferating the isolated cells through the cell culture until an amount of the cells reaches a desired amount, and mixing the proliferated cells with transplantable hydrogels to immediately transplant the resulting mixture into the human body, or culturing the cells in vitro in hydrogel for a certain period of time to transplant the obtained hydrogel cultures into the human body. According to this technique, the hydrogel transplanted in a sol state is converted into a gel state in vivo in the condition of the body temperature, and blood vessels are newly formed around the hydrogel while oxygen and nutrients are being supplied to cells due to the diffusion of bodily fluids. In this case, when blood is supplied, the cells are grown and divided to form a new tissue and organ. After a predetermined period of time, the hydrogel is released into the body or degraded, and eventually disappears.
The other technique is a method that includes mixing a certain drug with hydrogel to transplant the resulting mixture into the human body. In a transplanted site, the hydrogel in a sol state is converted into a gel state due to the body temperature. In this case, the drub is released at a proper concentration for a long time while the hydrogel is being slowly degraded.
Therefore, for such a tissue engineering study, it is, first of all, important to prepare a thermosensitive hydrogel similar to a biological tissue and may be converted into a gel state at or near the body temperature. Hydrogel used for regeneration of human tissues is maintained in a sol state near room temperature, but may be converted into a gel state near the body temperature. In this case, the cells should have cell affinity to form a tissue with a three-dimensional structure in the hydrogel, and play a role as an intermediate barrier positioned between the transplanted cells and host cells.
Examples of the representative hydrogels having such characteristics such as thermosensitivity include Pluronic (P. Holmqvist et al., Int. J. Pharm. 194: 103, 2000), poly-N-isopropylacrylamide (PNIPAAm) (M. Harmon et al., Macromolecules 36: 1, 2003), hyaluronic acid (HA) (M. Ogiso et al., J. Biomed. Mater. Res. 39: 3, 1998), linear polyethylene glycol (PEG)-poly(lactic-co-glycolic acid) copolymer (PLGA)-polyethylene glycol (PEG) (B. Jeong et al., J. Biomed. Mater. Res. 50: 2, 2000), linear polyethylene glycol (PEG)-poly(lactic acid) (PLA)-polyethylene glycol (PEG), star-shaped poly(lactic acid) (PLA)-polyethylene glycol (PEG), star-shaped poly-ε-caprolactone (PCL)-polyethylene glycol (PEG) (S. Zhao et al., J. Func. Polym. 15: 1, 2002), etc. However, the hydrogels listed above have drawbacks in that they relatively low mechanical properties, and have no sufficient cell affinity to be used for tissue regeneration.